The present invention relates to a display for three dimensional images.
Known display devices for producing three dimensional (3D) images create the illusion of a 3D opaque object by displaying a number of two dimensional (2D) images to the observer. Each of the 2D images is a view of the object from a particular direction and, during reproduction of the 3D image, each component 2D image is replayed in its respective direction.
The freedom of movement of the viewer location is limited by the total angular range over which the views are imaged. Known displays capable of imaging only a low number of 2D views provide a 3D image within a highly restricted range of viewing angles. Consequently the viewer is constrained to be within a limited range of positions in order to maintain the appearance of a 3D image. Similarly, the number of observers of a 3D image may also be restricted due to the limited number of 2D views.
"Subjective Assessments of the Resolution of Viewing Directions in a Multi Viewpoint 3D TV System", S. Pastoor, K. Schenke, p 217 Proc. SID Vol. 30/3 1989 describes the requirement for the number of views in a 3D display. It is estimated that, for a typical scene, 60 or more views may be required in an interocular spacing. For a wide field of view, several hundred views will have to be displayed at some time. It is currently not possible to achieve this with a simultaneous view presentation type of display.
A display described by Akiyama.K, and Tetsutani,N in a paper titled "Three dimensional visual communication" 1991 ITE Annual convention, p607, has a two view display produced by providing an interlaced image on a liquid crystal device (LCD) behind a lenticular screen. The position of an observer is monitored and, as the observer moves from an orthoscopic viewing zone to a pseudoscopic viewing zone, the sequence in which the images are interlaced is reversed so as to maintain the appearance of an orthoscopic image to the observer. Such a system requires precise tracking of the observer's head so as to determine the time at which the image sequence should be reversed. Further, such a display is limited to use by a single observer and the black mask of the LCD is made visible by the lenticular screen.
EP-A-0 404 289 "Television set or the like for creating a three dimensional perception of images and apparatus for creation of same" describes a 3D display in which a lenticular screen is moved with respect to a high resolution display device in response to movement of an observer. Such an apparatus requires very precise control of the motion of the lenticular screen and is limited for use by a single observer.
GB 2 206 763 discloses a 3D display apparatus of the temporally multiplexed type in which 2D images representing views taken from different directions are supplied to an LCD. A spatially modulated light source such as a cathode ray tube (CRT) is disposed in the focal plane of a lens disposed adjacent the LCD. Different regions of the CRT screen are illuminated in synchronism with the different 2D images displayed by the LCD so that the views are visible in the directions from which they were taken.